The present invention relates broadly to rotary cutting apparatus and, more specifically, to a router bit for selective attachment to a rotating machine with the router bit having interchangeable and adjustable knives.
At the outset, it should be noted that the term "knife" is used interchangeably with "blade" and "cutting tip" to define any assembly, device, or apparatus disposed at the endmost point of the router bit to provide cutting action on a workpiece. Further, while the present invention is more ideally suited for working wood and wood products, including fiberboard, chipboard, and MDF, the principles disclosed herein are equally applicable to cutting metal or any other material linked only in their susceptibility to cutting operations.
In working wood, it is often required to perform cutting or shaping operations, especially in panels and cabinet doors, to provided a contoured surface or other custom configuration. Typically, these operations are performed by machines known as copying machines using routers with both conventional, i.e., manual control or with computer numerical control (CNC).
Router bits used with such apparatus typically will utilize knifes having a shaped or profiled cutting edge or the edge may be straight. The knives are typically made using tool steel or solid carbide and can be fixed to a cutter head using screws so that they can be dismounted, resharpened, and interchanged.
Typically, the router bits for profiling and boring with profiled knives are formed of a single steel block wherein seats for the knives are machined.
The removable or interchangeable knives offer several advantages over knives which are brazed, welded, or otherwise permanently affixed to the router bit. Obviously, an advantage is that the knives may be interchanged when worn or removed and resharpened to reform the profile. However, certain disadvantages are present. Initially, the advantages associated with resharpening are somewhat offset by the reduction of cutting diameter imposed by the reduction of knife size during sharpening. Therefore, small diameters may not be possible with resharpened knives. Further, the knives may be difficult to reposition in their original orientation on the bit, resulting in a poor finish on the workpiece. There also exists a safety hazard should the knives come loose during cutting operation and, finally, the knives typically offer poor chip unloading performance.
However, brazed or otherwise permanently mounted knives offer the advantage of safety and improved initial balancing yet present several problems of their own. Initially, any resharpening of the knives will cause a loss of the original diametrical dimensions. Further, the bits themselves must be interchanged when different profiles are to be cut. Finally, when the knives are worn, the entire router bit must be replaced.